Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, Elche, Spain.
PLoS One. 2013;8(1):e53378. doi: 10.1371/journal.pone.0053378. Epub 2013 Jan 8.
The Arabidopsis rugosa1 (rug1) mutant has irregularly shaped leaves and reduced growth. In the absence of pathogens, leaves of rug1 plants have spontaneous lesions reminiscent of those seen in lesion-mimic mutants; rug1 plants also express cytological and molecular markers associated with defence against pathogens. These rug1 phenotypes are made stronger by dark/light transitions. The rug1 mutant also has delayed flowering time, upregulation of the floral repressor FLOWERING LOCUS C (FLC) and downregulation of the flowering promoters FT and SOC1/AGL20. Vernalization suppresses the late flowering phenotype of rug1 by repressing FLC. Microarray analysis revealed that 280 nuclear genes are differentially expressed between rug1 and wild type; almost a quarter of these genes are involved in plant defence. In rug1, the auxin response is also affected and several auxin-responsive genes are downregulated. We identified the RUG1 gene by map-based cloning and found that it encodes porphobilinogen deaminase (PBGD), also known as hydroxymethylbilane synthase, an enzyme of the tetrapyrrole biosynthesis pathway, which produces chlorophyll, heme, siroheme and phytochromobilin in plants. PBGD activity is reduced in rug1 plants, which accumulate porphobilinogen. Our results indicate that Arabidopsis PBGD deficiency impairs the porphyrin pathway and triggers constitutive activation of plant defence mechanisms leading to leaf lesions and affecting vegetative and reproductive development.
拟南芥 rugosa1（rug1）突变体的叶片形状不规则，生长受阻。在没有病原体的情况下，rug1 植株的叶片会自发出现病变，类似于病变模拟突变体中看到的病变；rug1 植物还表达与防御病原体相关的细胞学和分子标记。这些 rug1 表型在黑暗/光照转换时会变得更强。rug1 突变体也有开花时间延迟、 floral repressor FLOWERING LOCUS C (FLC) 上调以及开花促进剂 FT 和 SOC1/AGL20 下调的现象。通过抑制 FLC，春化作用抑制了 rug1 晚开花的表型。微阵列分析显示，rug1 和野生型之间有 280 个核基因表达差异；其中近四分之一的基因参与植物防御。在 rug1 中，生长素反应也受到影响，几个生长素反应基因下调。我们通过基于图谱的克隆鉴定了 RUG1 基因，发现它编码卟胆原脱氨酶（PBGD），也称为羟甲基胆素合酶，是四吡咯生物合成途径中的一种酶，该酶在植物中产生叶绿素、血红素、胆色素和植物色素obilin。rug1 植物中 PBGD 活性降低，卟胆原积累。我们的结果表明，拟南芥 PBGD 缺乏会损害卟啉途径，并触发植物防御机制的组成性激活，导致叶片病变，并影响营养和生殖发育。
